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Module « scipy.signal »

Fonction lp2bs - module scipy.signal

Signature de la fonction lp2bs

def lp2bs(b, a, wo=1.0, bw=1.0) 

Description

help(scipy.signal.lp2bs)

Transform a lowpass filter prototype to a bandstop filter.

Return an analog band-stop filter with center frequency `wo` and
bandwidth `bw` from an analog low-pass filter prototype with unity
cutoff frequency, in transfer function ('ba') representation.

Parameters
----------
b : array_like
    Numerator polynomial coefficients.
a : array_like
    Denominator polynomial coefficients.
wo : float
    Desired stopband center, as angular frequency (e.g., rad/s).
    Defaults to no change.
bw : float
    Desired stopband width, as angular frequency (e.g., rad/s).
    Defaults to 1.

Returns
-------
b : array_like
    Numerator polynomial coefficients of the transformed band-stop filter.
a : array_like
    Denominator polynomial coefficients of the transformed band-stop filter.

See Also
--------
lp2lp, lp2hp, lp2bp, bilinear
lp2bs_zpk

Notes
-----
This is derived from the s-plane substitution

.. math:: s \rightarrow \frac{s \cdot \mathrm{BW}}{s^2 + {\omega_0}^2}

This is the "wideband" transformation, producing a stopband with
geometric (log frequency) symmetry about `wo`.

Examples
--------
>>> from scipy import signal
>>> import matplotlib.pyplot as plt

>>> lp = signal.lti([1.0], [1.0, 1.5])
>>> bs = signal.lti(*signal.lp2bs(lp.num, lp.den))
>>> w, mag_lp, p_lp = lp.bode()
>>> w, mag_bs, p_bs = bs.bode(w)
>>> plt.plot(w, mag_lp, label='Lowpass')
>>> plt.plot(w, mag_bs, label='Bandstop')
>>> plt.semilogx()
>>> plt.grid(True)
>>> plt.xlabel('Frequency [rad/s]')
>>> plt.ylabel('Amplitude [dB]')
>>> plt.legend()

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